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Flashcards in KEY TERMS Deck (22)
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1

Interference?

When two (or more) waves superpose/meet at a point - there is a change in overall displacement

2

Coherent?

Constant phase difference (between the waves)

3

Emission line spectra?

Where each element produces a unique emission line spectrum because of its unique set of energy levels

4

Continuous spectra?

All visible frequencies/wavelengths are present (e.g. of a lamp filament)

5

Absorption line spectra?

A series of dark spectral lines against the background of a continuous spectrum

6

Absolute scale of temp?

A scale for measuring temp based on absolute zero and the triple point of water (the difference between 1K-2K is the same as that of 1-2 degrees Celsius)

7

Absolute zero?

The lowest possible temperature - the temperature at which substances have minimum internal energy

8

Absorption/attenuation coefficient?

A measure of the absorption of X-ray photons by a substance (m^-1)

9

Acceleration?

The rate of change of velocity

10

Acceleration of free fall?

The rate of change of velocity of an object falling in a gravitational field (g)

11

Acoustic impedance?

The product of the density - of a substance - and the speed of ultra sound in that substance (Z, or Kgm^-2s^-2)

12

Acoustic/impedance matching?

The use of two substances with similar acoustic impedance to minimise reflection of ultrasound at the boundary between them

13

Activity?

The rate at which nuclei decay/disintergrate in a radioactive source - measured in becquerels/Bq or decays per second

14

Alpha radiation?

Ionising radiation consisting of particles made up two protons and two neutrons - a helium nucleus with Q=+2e

15

Amount of substance?

A measure of the amount of matter in moles

16

Ampere?

Base unit of electric current - the current flowing in two parallel wires in a vacuum 1m apart, so that there is an attractive force of 2.0 x 10^-7 N per metre length of wire

17

Amplitude?

The maximum displacement from the equilibrium position (pos or neg)

18

Angle of incidence?

The angle between the direction of travel of an incident wave and the normal at a boundary between two media

19

Angle of reflection?

The angle between the direction of travel, of a reflected wave, and the normal at a boundary between two media

20

Angular frequency?

A quantity used in oscillating motion - it equals the product of 2 x pie x frequency

21

Angular velocity?

The rate of change of an angle for an object moving in a circular path

22

Anion?

A negatively charged ion - attracted to the anode